Northern Plains American Indians have the highest tobacco use compared with other American Indians and non-Hispanic Whites. Notably, the rate for tobacco related cancers also are higher among Northern Plains American Indians as compared to American Indians living in other regions and for non-Hispanic Whites living in the Northern Plains and elsewhere in the US. Although awareness of these elevated rates of tobacco-related cancers is well known throughout American Indian communities, Northern Plains American Indian adults continue to use tobacco. In addition, Northern Plains American Indian patients with cancer continue to smoke despite knowing that this behavior is related to cancer recurrence, new cancers and other chronic illnesses. Rapid City Regional Hospital's (RCRH) mission is to reduce cancer mortality among American Indians in the Northern Plains. In 2002, Dr. Petereit, the PI for this project, developed the Walking Forward Program which is designed to address cancer disparities among Western South Dakota tribes. To accomplish this, Community Research Representatives have been hired to work with the reservation-based Cheyenne River Sioux, Rosebud Sioux, and Pine Ridge Lakota Sioux and the Rapid City urban Indian community. This study will focus on American Indians living on the Cheyenne River, Rosebud and Pine Ridge Reservations. The proposed project, American Indian mHealth Smoking Dependence Study (PQ4), is designed to answer the research question, Why don't Northern Plain American Indians alter tobacco use behaviors known to increase the risk of cancer? The study is based on the Theory of Planned Behavior and uses a phase- based framework. mHealth (mobile health), the use of wireless devices such as cell phones to provide health- related information, will facilitate attainment of project aims as it offers a low-cost, efficient way to provide health-related messages to rural and other populations. This will be feasible for this study as access to wireless technology is rapidly increasing among Northern Plains American Indians. The specific aims for the study are: Aim 1: Measure factors that predict smoking behaviors among Northern Plains American Indians; Aim 2: Identify issues and risk factors related to smoking persistence and high relapse behaviors, regardless of knowledge about smoking hazards, among Northern Plains American Indians; and Aim 3: Using the Theory for Planned Behavior, develop and adapt existing tobacco cessation interventions for use with adult Northern Plains American Indians who smoke cigarettes daily. Outcome data will reveal predictors of intention to quit smoking, successful quit attempts, and relapse. Other social cognitive variables that ensure initial quit attempts are translated into longer term abstinence wil be identified. Study results will impact tobacco use among Northern Plains American Indians by providing insight into designing effective cessation interventions for this population.